The focus of this proposal is an understanding of the mechanisms leading to sleep apnea by evaluating the structure and function of the upper airway using state-of-the-art magnetic resonance imaging techniques. We have utilized novel implementations of state-of-the-art dynamic magnetic resonance imaging and tagging techniques coupled with p hysiologic monitoring of respiration during wakefulness and sleep to evaluate upper airway structure and function in patients with sleep apnea. These studies have begun to elucidate the biomechanics and compliance of the upper airway, and in particular determine the anatomic structures whose mortion underlies the dimensional changes that take place in the upper airway during respiration, and during airway closure during sleep. Our overall hypothesis is that the key structures mediating changes in airway size during respiration, sleep, and during apneas are the lateral pharyngeal walls. Customized computer graphics-based volumetric image analysis and display methods provide for objective quantitation of the image data. Improved understanding of the functional and mechanical airway abnormalities in patients with obstructive sleep apnea should lead to new treatment strategies for this disorder.